Vehicles such as cars and trucks are susceptible to damage from gravel and other road debris. Various protective measures have been taken to reduce paint chipping and other vehicle damage, including the application of protective urethane sheets or films over the areas of vehicles that are most likely to be damaged. The effectiveness of such protective sheets and films may be demonstrated by projecting gravel against protected and unprotected areas of a painted panel, and comparing the resulting damage in the protected and unprotected areas.
Standard tests have been developed to measure paint chipping resistance. For example, the ASTM Standard Test Method for Chipping Resistance of Coatings, ASTM D3170-12, is a test procedure where standardized road gravel is projected within an enclosed cabinet or module by means of a controlled air blast onto a test specimen. In accordance with the ASTM D3170-12 test, air that has been pressurized to 70 psi is released through a valve and is used to project the gravel toward the test specimen. The test specimen may then be analyzed to determine the amount of chipping of the painted surface.